Mindy McCready's ex-boyfriend Billy McKnight and former associates, retired baseball player Roger Clemens and Dr. Drew Pinsky of "Celebrity Rehab," have weighed in on her shocking death.

The singer was found dead after an apparent suicide via a self-inflicted gunshot to the head on Sunday, February 17. She was 37 years old and leaves behind two children -- Zander, 6, and Zayne, who is nine months old.

McCready had undergone rehab -- the latest in many past stints -- earlier this month and her children were placed in foster care in Arkansas. Their whereabouts were not made public at the time of her death. Zander's father is McKnight.

He and McCready had a turbulent relationship. He witnessed her attempt suicide twice, following arguments. In 2005, he was charged with attempted murder and aggravated burglary after allegedly breaking into her home and assaulting her. She was treated at a hospital. He pleaded guilty to assault and spent 30 days behind bars. The two continued their relationship, despite a court order.

"Well, as sad as it is, it didn't come as a major shock because she's just been battling demons for long and of course I was around her when she attempted suicide twice, so I knew it was in her," McKnight said on NBC's "Today" show on Monday, February 18. "I feel for her mother and family and especially my son. But I can't say that it shocked me, no."

McCready lost custody of Zander in 2008, after several unrelated arrests and a jail stint on her own. Following a court battle with her mother, who had been caring for the child in Florida, she regained custody in December.

McKnight told the "Today" show that the boy "shouldn't have been taken from me to begin with" and that he can provide for him. He has not filed any official requests for custody of the child, who remains in foster care in Arkansas, but says that he would like to make sure he remains close to his baby brother.

"Enough is enough," he said. "He's up there all alone. He has no family in Arkansas. He has plenty of family who love him here -- cousins, aunts, uncles. He needs to come home."

McCready had died just a month after her boyfriend David Wilson, the father of her youngest son Zayne, who is nine months old, died of an apparent gunshot wound at their home. Police had begun an investigation into his death, which McCready said was a suicide.

"And Zayne, I dunno what's going to happen with Zayne, but if he does go to Fort Myers, where her family is from, it's only an hour and a half difference," McKnight added. "I'd like to keep those boys being brothers together and try to turn my son's life around. He's had a rough first six years and he deserves better than this. My heart is broken right now. I'm very worried."

Roger Clemens - "Yes, this is sad news"

In 2008, McCready told "Inside Edition" that she dated Clemens, a former player for the New York Yankees, for about 10 years. She said she met him at a karaoke bar when she was 16 and he was 28 and that they didn't have sex until several years later.

Clemens, who was and is still married, had via his lawyer said she was a family friend but denied having had any "inappropriate or improper relationship" with the singer.

On Monday, a day after her death, Clemens, who is now an instructor for the Houston Astros, issued to reporters a typed statement, which was posed on the official MLB website.

"Yes, this is sad news," he said. "I had heard over time that she was trying to get peace and direction in her life. The few times that I had met her and her manager/agent they were extremely nice."

Dr. Drew Pinsky - "My heart goes out to Mindy's family and children"

McCready had battled drug and alcohol addictions for years and underwent several stints in rehab, the latest just two weeks before her death. She appeared on season 3 of "Celebrity Rehab," Drew's VH1 show featuring celebrities battling addictions, in 2010.

"I am deeply saddened by this awful news," Pinsky said in a statement about McCready's death via the cable network. "My heart goes out to Mindy's family and children. She is a lovely woman who will be missed by many."

"Although I have not treated her for few years, I had reached out to her recently upon hearing about the apparent suicide of her boyfriend and father of her younger children," Pinsky added. "She was devastated. Although she was fearful of stigma and ridicule she agreed with me that she needed to make her health and safety a priority. Unfortunately it seems that Mindy did not sustain her treatment."

Mackenzie Phillips - "My heart is breaking"

During one episode of "Celebrity Rehab," her on-screen roommate, Mackenzie Phillips, witnessed her suffering a seizure -- a side-effect of her detoxing.

McCready is the fifth former cast member who has died unexpectedly and the third from season 3. For decades, research has suggested that substance abuse and psychological disorders, namely depression, are among the many contributing factors that can increase a person's risk of suicide.

The four previous "Celebrity Rehab" stars who had taken their lives are:

4. Rodney King - the man who became an historical icon and symbol of police brutality and U.S. racial tension due to a 1991 videotaped beating died in June 2012 at age 47 of accidental drowning in his swimming pool, while PCP, cocaine and alcohol were determined to be contributing factors. He appeared on season 2 of "Celebrity Rehab" in 2008 and later starred on its spinoff, "Sober House."

(Pictured above: Dr. Drew Pinsky speaks to OTRC.com on Feb. 24, 2011l at a party honoring the Top 24 "American Idol" finalists in Los Angeles.)